European Journal of Wood and Wood Products最新文献

The paper presents a fully Lagrangian mesh-free solver to simulate the dynamic behavior of post-tensioned timber structures. Weakly Compressible Smoothed Particle Hydrodynamics (SPH) is employed to model both the timber and the tendon. An efficient and simple coupling method between the timber and the tendon is proposed by considering the numerical stability. Besides, the same coupling algorithm is used to model the interaction between column and beam elements. Although the column is treated as rigid in the simulations, the coupling algorithm accounts for the initial compression of the column resulting from post-tensioning. For the verification of the code for solids and material nonlinearity of timber, benchmark problems available in the literature are used. Finally, the solver's capability is demonstrated through dynamic analysis of post-tensioned timber structures. The solutions obtained for all the cases are in good agreement with the experimental and theoretical data, which indicates the applicability and accuracy of the solver.

This paper presents the dynamic characteristics of the glued-laminated-timber (glulam) floor within China's tallest timber office building and establishes a Finite Element (FE) model. The veracity of the FE model is substantiated through experimental validation. The investigation delves into the impact of variations in the dimensions of Reinforced Ribbed Wood Beams (RRTB) on floor vibration characteristics and assesses the comfort index. Both Ambient Vibration Test (AVT) and human walking tests were carried out on the specific floor under scrutiny. The results show that the RRTB significantly increase the overall stiffness of the floor, and change the natural frequency and modal vibration shape of the floor. The thickness of the RRTB exerts a more pronounced impact on the dynamic characteristics of the floor in comparison to its width. The static deflection of the floor proves to be the most responsive parameter to alterations in the size of the RRTB, compared to the fundamental frequency and maximum displacement. For high-rise glulam building floors, AVT can be effectively applied to fundamental frequency testing; Even if the fundamental frequency of the floor meets the comfort index, supplementary acceleration and velocity amplitude tests remain imperative.

Not before the year 2016, the European standard system did allow for classifying the durability of treated wood in addition to natural durability of untreated wood species. After its latest revision, EN 350 (2016) allows a durability classification of solid wood and wood-based materials with the help of five durability classes (DC) between ‘very durable’ (DC 1) and ‘non-durable’ (DC 5). However, different test methods, assessment measures, and calculation methods can be used for durability classification. This inevitably leads to different assessments of the biological durability of wood. This study aimed therefore on a comparative durability classification of preservative-treated and chemically modified wood (here: treated with 1,3-dimethylol-4,5-dihydroxyethyleneurea, DMDHEU) using different laboratory and field test methods. Durability classes of the tested timbers differed not only between tested materials, but depended also on the applied test, assessment, and calculation method. In this respect, the use of relative values (x-values), i.e., mass loss (ML) or MOE loss data compared with a non-durable reference material can help to harmonize the classification and make DCs more comparable. The use of relative values can also help to reduce the effect of varying virulence of test fungi, activity of test soil substrates, and the climate-induced hazard of test sites.

Cork planks with Yellow Stain (YS) defect are rejected from cork-stopper factory industries resulting in large economical losses. This defect has been related to 2,4,6—trichloroanisole (TCA), a chemical compound responsible for an off-flavor aroma in wine known as cork taint. The relation between YS and TCA was confirmed by the analyzes carried out in this work. Considering that fungi have the capacity to convert trichlorophenol into TCA, raw cork planks were collected in a factory and the mycobiota was searched using morphological and molecular methods. Eight genera and order of fungi were obtained and statistical analysis revealed that the Trichoderma genus is significantly related to TCA levels critical for industry, in particular the species Trichoderma atrobrunneum, a fungus belonging to Trichoderma harzianum complex. To our knowledge, this is the first report associating T. atrobrunneum to high TCA levels and YS defect of cork.

Bamboo nodes are an important component for increasing the hardness and stability of growth. However, little is known about how bamboo nodes affect resistance to biological control agents for industrial use. This study aims to analyze the durability differences between node and internode structures against subterranean termites. Two bamboo species, Giganthochloa scortechinii and Giganthochloa levis were investigated to determine their resistance against Coptotermes curvignathus in laboratory (no-choice and choice) and above-ground experiments. Samples measuring 25 mm × 25 mm x bamboo thickness and 100 mm × 40 mm x bamboo thickness were taken from the three portions (bottom, middle, and top) and each portion was subdivided into two parts: nodes and internodes. Moisture content is also determined for each portion and part. Overall, G. scortechinii is more resistant to C. curvignathus than G. levis, and the node section has greater resistance compared to the internode. The resistance of both bamboo species tested increases towards the top of the node and the internode. The weight loss decreases towards the top in all tests, while the nodes show less weight loss compared to the internodes. The visual determination value for G. scortechinii is 7.4 to 9.0 (choice) and 7.5 to 9.2 (no-choice), while 6.6 to 7.5 (choice) and 6.5 to 7.4 (no-choice) for G. levis. The high resistance of the nodes compared to the internodes is closely related to the anatomical structure of the individual parts and the position in the stem.

Parinari curatellifolia is the main species used to produce charcoal in Angola. Its chemical, anatomical, and thermal properties were analyzed. The bark is dark grey, rough, and corky, and the wood is brown to yellow-red. Compared to wood, bark fibers presented lower length, lumen, and wall thickness. There is not much difference between height and cell numbers of rays. Sieve tube elements appear solitary or in small groups (2–3 cells), and vessels were of two diameter classes but diffuse-porous. Bark basic density was lower than wood (505 kg.m^− 3vs. 580 kg.m^− 3). The mean chemical composition from bark vs. wood of P. curatellifolia was ash (3.2% vs. 1.6%), total extractives (12.2% vs. 10.0%), total lignin (42.4% vs. 28.4%), and suberin 5.4%. Families identified by GC-MS from DCM extracts were predominated by fatty acids in wood and triterpenoid contents in bark. Bark and wood had higher antioxidant activity in FRAP and DPPH methods. The bark had a monomeric lignin composition richer in guaiacyl-units (25.9% vs. 22.5%) and lower syringyl-units (5.7% vs. 8.5%). Potassium was the most abundant mineral, while the least was cadmium found in wood and bark. Regarding thermal properties, bark presented higher moisture content (9.0% vs. 8.0%), ash (3.33% vs. 1.61%), total volatiles (27.5% vs. 20.7%), lower fixed carbon (69.1% vs. 77.7%) and higher heating value (20.9 MJ/kg vs. 19.1 MJ/kg). According to these characteristics, both biomasses are interesting for developing more value-added products (e.g., charcoal, bio-chemicals with phytochemistry and pharmacology activities) besides burning under the context of biorefineries.

While traditional wood preservatives may impede wood decay, their potential harm to both human health and the environment has led to limitations in their usage. This has spurred recent research to focus on seeking wood preservatives derived from plants, owing to their inherently eco-friendly attributes. Agricultural waste such as corn stover fractions, are not only abundant but also frequently underutilized, making them promising candidates for such endeavors. This study delves into the antifungal properties of extracts derived from thermally degraded corn stalk and corn cob. The selection of optimal raw materials and the identification of the most effective thermal degradation process were determined based on their inhibitory activity against Gloeophyllum trabeum (Pers.: Fr.) Murr. and Trametes versicolor (L. ex Fr.) Quél. Gas chromatography-mass spectrometry (GC-MS) was employed to analyze the composition of corn cob extracts resulting from various thermal degradation processes. The evaluation of decay resistance involved wood decay resistance tests and electron microscope observations. Results indicated that ethanol extracts from corn cobs heat-treated at 220 °C exhibited the strongest antifungal activity, accompanied by the highest extract yield. Additionally, the corn cob extracts also demonstrated inhibitory effects on the growth of Aspergillus niger, Escherichia coli, and Staphylococcus aureus. Chemical analysis revealed significant quantities of vanillin, squalene, and other compounds known for their antifungal or antibacterial activity in the corn cob extracts. Furthermore, wood treated with these extracts exhibited improved decay resistance, surpassing that against G. trabeum compared to T. versicolor. These findings suggest that thermally degraded corn cob extracts can be utilized as environmentally friendly wood preservative.

Coating paper with cellulose micro/nanofibrils (CMF/CNF) can improve the performance of paper packaging. However, the cost of the process is high due to the significant energy consumption during the CMF/CNF production process, which can be reduced through pre-treatment of cellulosic fibers. The objective of this work was, therefore, to evaluate the performance of CMF/CNF subjected to accelerated carbonation with different concentrations of calcium hydroxide (5% and 10% m/m) as a paper coating for packaging production in terms of spreading properties of adhesives, air permeability, and water absorption. The CMF/CNF coating was able to fill pores contained in the papers, with the treatment with 10% carbonation (CMF/CNF 10%) being the one that adhered best to the surface. There was a reduction in surface roughness from 1.35 ± 0.53 μm (uncoated paper) to 0.72 ± 0.21 μm (CMF/CNF 10%). Similarly, air permeability in the coated treatments was decreased, indicating good barrier properties and possible CO₂ absorption activity in the carbonated samples. Coated papers showed greater spreading of water, PVA, and PVOH. On the other hand, the Cobb value dropped from 41.55 ± 3.83 g m² (uncoated paper) to 26.26 ± 2.36 g m² (CMF/CNF 10%). CMF/CNF subjected to pre-treatment with accelerated carbonation have the potential for use as a coating material, being recommended for applications in food packaging and those that will be subjected to gluing/coating processes with other materials.

This work uses the M-theta method on a new proposed specimen called "I-specimen" for the numerical modeling of cracks on some tropical hardwoods in general and in particular on some Cameroonian woods. The finite element analysis of fracture in an orthotropic medium is developed. The fracture algorithm is introduced in a finite element software Cast3M and, with an incremental orthotropic formulation, the simulation of crack growth is computed. Using this method, stress intensity factors and energy release rate are calculated for Mode I and II failures. The energy release rate and stress intensity factors are numerically deduced using “I-specimen” to characterize three Cameroonian hardwoods under mode I and II loading for different crack growths. The specimen used has better characteristics than other samples generally used in the literature and its geometry is very simple to define. The proposal of a new geometry that can guarantee the reproduction of the different failure modes while exhibiting some stability of the crack parameters G and K during propagation was evaluated and compared to other specimens given by the fracture mechanics literature. For each fracture mode, the influence of the orthotropy rate parameters on the energy release rate was investigated.

The fire performance of buildings can be assessed through the thermal and charring characteristics of laminated bamboo lumber (LBL), due to its combustibility properties, which are akin to those of wood. This study employed Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Hot Disk techniques to ascertain the thermal conductivity, heat flow, and mass loss rate of LBL at elevated temperatures. Thermal conductivity initially rises, then falls, as the temperature increases from 25 °C to 280 °C across both grain directions, peaking at 100 °C. The thermal conductivity ratio of LBL, from parallel to perpendicular to grain, ranges from 1.93 to 4.00. A distinct peak in heat flow of LBL, ranging from 1.00 to 2.23, is observed as the temperature increases from 23 °C to 200 °C. Beyond 200 °C, the mass loss rate of LBL accelerates, driven by the pyrolysis of phenolic resin and decomposition of bamboo cellulose. The normal and nominal charring rates for LBL specimens were established based on the detachment of charring layers at furnace temperatures, adhering to ISO 834 standards. These findings may serve as a foundation for advanced fire performance analysis of LBL structures.